In previous studies, we have shown that gold deposited on a monolayer
(ML) of graphene on SiC(0001) is intercalated below the ML after an
annealing procedure and affects the band structure of graphene. Here we
prove experimentally and theoretically that some of the gold forms a
dispersed phase composed of single adatoms, being intercalated between
the ML and the buffer layer and in a hollow position with respect to C
atoms of the ML on top. They are freestanding and negatively charged,
due to the partial screening of the electron transfer between SiC and
the ML, without changing the intrinsic n-type doping of the ML. As these
single atoms decouple the ML from the buffer layer, the quasiparticles
of graphene are less perturbed, thus increasing their Fermi velocity.
Moreover, the hollow position of the intercalated single Au atoms might
lead to spin-orbit coupling in the graphene layer covering IC domains.
This effect of spin-orbit coupling has been recently observed
experimentally in Au-intercalated graphene on SiC(0001) D. Marchenko,
A. Varykhalov, J. Sanchez-Barriga, Th. Seyller, and O. Rader, Appl.
Phys. Lett. 108, 172405 (2016) and has been theoretically predicted for
heavy atoms, like thallium, in a hollow position on graphene C. Weeks,
J. Hu, J. Alicea, M. Franz, and R. Wu, Phys. Rev. X 1, 021001 (2011); A.
Cresti, D. V. Tuan, D. Soriano, A. W. Cummings, and S. Roche, Phys. Rev.
Lett. 113, 246603 (2014).